1. Field of the Invention
This invention relates generally to preparing the end of a hydraulic or other reinforced hose to receive a coupling, and, more specifically, to the simultaneous skiving of the outer and inner surfaces of a hose end.
2. Background
High pressure hydraulic and pneumatic hoses are typically constructed with one to six layers of spiral wrapped steel wire reinforcement embedded in the walls. A simplified model useful for conceptualization is an inside rubber tube spirally wrapped with steel wire, covered by an outer rubber tube. In practice, the parts of the hose are bonded together, more or less as reinforced tire parts are bonded, into a single unit.
The hose is usually manufactured in long lengths supplied in coiled form to manufacturers who cut to the desired length. Connectors or "fittings" are fastened to the ends of hoses to allow convenient and leak free coupling. Fittings are available in many styles for differing applications and preferences. Two classes of connectors are "reusable" and "crimp" fittings.
Reusable fittings consist substantially of two parts, a "socket" which slips over the outside of a prepared hose and threads onto the second part, a "nipple" which has a tube that slips inside the prepared hose. Crimp fittings are similar except that threads are omitted and slips inside the prepared hose. Crimp fittings are similar except that threads are omitted and the outer socket is of thinner steel material which may be squeezed and formed (crimped) to tightly secure the fitting to the end of the hose. Some of the same equipment and processes apply to both types of fittings.
In preparation for attaching certain fittings, some rubber material is removed from both the outside diameter and the inside diameter of the hose. This preparation serves to minimize the outside diameter of the fitting, minimize flow restriction by increasing the inside diameter of the hose before inserting the nipple, and strengthen the fitting's grip on the hose.
For high pressure applications, reusable fittings typically require skiving the outside of the hose only, while crimp fittings typically require removing a portion of both the inside and the outside of the hose. Thus, the present invention has its primary application in preparing hose ends for installation of crimp fittings, although it is not limited to this application.
The process of removing a portion of either the outer or inner surfaces of a hose end is called skiving. External skiving compares to stripping or peeling. Internal skiving compares to boring or reaming. Heretofore, devices and methods for skiving have focused singularly on preparing either the outer diameter or inner diameter of the hose end, but not both.
The most elementary way to skive the outer surface of reinforced hose is with knife and pliers. The knife and pliers method is a manual method where a ring is cut around the hose end with a knife down to the wire reinforcement braid and a slit is made from the ring to the hose end. The outer layer of rubber is then peeled off with pliers. To speed up the process, special "external skiving tools" have been developed, and are well-known in industry.
One well accepted external skiving tool consists of three major parts. The first part is a mandrel with a beveled nose which fits inside the hose to steady it and allow precise control of the cutting depth. The mandrel also has a machined stop to control the length of hose to be skived. The tail end, beyond the stop, is a gripping portion, normally cylindrical, made to be gripped in a spindle. An angled bracket is clamped to the mandrel. It extends from the axis of the mandrel to clamp and hold an outer diameter cutting tool normal to the surface of the hose. The cutting tool is adjusted and clamped to skive the outside of the hose. As the tool is turned and the mandrel is inserted into the end of a hose, the cutting tool makes a cut normal to the hose with one cutting blade, and a second cut to skin or skive the hose with another blade.
Prior methods of skiving the outside diameter of a hose end with the described external skiving tool are:
(a) manual--An appropriate sized skiving tool for the hose size is selected and mounted in a vise. The hose end is slipped over the mandrel until the hose contacts the skiving blade of the outer diameter cutting tool. The hose is pushed and turned clockwise to skive the outside diameter until the hose bottoms on the stop. The tool is withdrawn and the hose end cleaned. PA1 (b) manual with "speed handle"--The hose is clamped in a vise and the skiving tool is attached to a "speed handle," a device similar to the brace of a hand drill. The mandrel is pushed into the hose and turned clockwise with the speed handle until the mandrel stop bottoms on the hose. The tool is withdrawn and the hose end cleaned. PA1 (c) by machine--The skiving tool is mounted in the spindle of a turning machine and the spindle is started counterclockwise (as looking at the spindle from the front). The hose is pushed over the mandrel of the skiving tool by hand, preferably mounted in a vise which slides parallel to the axis of the spindle, until the hose bottoms on the mandrel stop. The hose end is then withdrawn and cleaned. PA1 (a) manual--The appropriate sized skiving tool is selected and clamped in a vise. The hose is pushed over the end of the skiving tool until it contacts the cutting threads. The hose is pushed and turned counterclockwise until it bottoms on the tool. The hose end is then withdrawn and cleaned. PA1 (b) manual with "speed handle"--The hose is clamped in a vise while the tool is attached to a speed handle. The tool is then inserted into the hose end and turned counterclockwise with the speed handle until it bottoms on the hose. The tool is withdrawn and the hose end cleaned. PA1 (c) by machine--The skiving tool is mounted in the spindle of a turning machine and the spindle started clockwise (as looking at the spindle from the front). The hose is pushed over the mandrel of the skiving tool by hand, preferably mounted in a vise which slides parallel to the axis of the spindle, until the hose bottoms on the stop. The hose end is then withdrawn and cleaned.
Special tools called "internal skiving tools" are likewise well-known in the industry for trimming the inner surface of a hose end. The typical internal skiving tool has a nose portion with a beveled end for easy insertion into the hose end. Behind the nose are sharpened threads which screw into the inside wall of the hose and cut it. A stop on the tool aids skiving to the desired depth from the end of the hose. A desired cylindrical ring section is pulled out when the tool is retracted. The tail end, beyond the stop, is a gripping portion which may be hexagonal for secure gripping in a spindle, or vise.
Prior methods of skiving the inside diameter of a hose end with the described internal skiving tool are:
In the patent art, Rassi and Dick, in U.S. Pat. No. 3,759,121, describe a self-contained machine including dual opposed chisel-type cutters for skiving the outside of a hose end. Beckhausen, in U.S. Pat. No. 3,811,347, discloses a device with guide rods and rollers and one or more cutting blades to strip material from the outside of a hydraulic hose end. Anderson et al., in U.S. Pat. Nos. 3,820,421 and 3,938,215, describe an apparatus for skiving the outside of the end of a piece of reinforced hose while vacuuming the inside of the hose to recover particulate debris. U.S. Pat. No. 3,965,570 to Kozulla discloses a tool for skiving the outside diameter of the end of a hydraulic hose with an adjustable chisel-type cutter and a mandrel which fits inside the hose for support. Plies, in U.S. Pat. No. 4,000,552, describes a machine which buffs the exterior surface of the end of a hose with a wire brush to make the exterior concentric with the interior and to prepare it for a coupling.
An important limitation of conventional skiving devices and methods is that the outer and inner hose end surfaces must be prepared in separate operations. None of the known skiving apparatus is capable of performing double duty as both an outer and inner diameter skiving tool, much less simultaneously skiving both the inner and outer hose end surfaces. This requirement of multiple skiving operations increases handling time, adds to equipment requirements, and decreases worker productivity.
It is thus an object of the present invention to provide a device and method for the simultaneous skiving of both the outside and inside of a hose end.
It is a further object of the invention that the device be capable of use with conventional turning machines, such as portable reusable hose assembly machines, operating, for example, at 15 rpm.